The 1964 model De Havilland DHC-2 Beaver was chartered by FTSE 100 chief executive Richard Cousins on New Year's Eve before it nose dived into a river outside Sydney, killing him, his fiancee Emma Bowden, 48, her 11-year-old daughter and his two sons as well as the pilot.

The Telegraph reported that the same model aircraft crashed into the ground in Canada in August 2015 following a steep turn, killing the pilot as well as Fiona Hewitt, 52, her husband Richard, 50, and children Harry, 14 and Felicity, 17, all from Milton Keynes.

Back then, an accident report by Transportation Safety Board of Canada said that there had been nine fatal accidents involving the DHC-2 Beaver after incidents in which they stalled and crashed.

The TSB recommended a stall warning system be fitted into all the DHC-2 aircraft in Canada. Investigators in Australia are piecing through the wreckage of Sunday's crash in Hawkesbury River, near the suburb of Cowan.

Kevin Bowe, vice-president of the Seaplane Pilots Association Australia, told Sydney's Daily Telegraph the plane may have hit an unexpected pocket of air and a downdraft may have caught the pilot out.

Aaron Shaw, the managing director of Sydney Seaplanes, said weather conditions for the flight were perfect, the plane's engines had been checked, and the pilot was experienced.

"These aircraft are some of the most widely used sea planes in the world to this day. They are checked over at the end of each day. Every 100 hours of flying time they're taken out of the water into a hangar or an area for regular maintenance.

"The engines are required to be replaced every 1,200 hours - we replace ours at 1,100 hours and the engine on this aircraft was 200 hours old," he said.

Richard Cousins was the chief executive of Compass, the world's largest contract catering company.

Ian Thorpe, the brother of Cousins' first wife Caroline, paid tribute to his former brother-in-law and nephews.

"I look back and I'm very proud of all of them. I feel thrilled to have known them, they've been wonderful people. It's a huge shock knowing they're no longer there. I never thought I'd start 2018 like this. Never ever," he told Sky News.